include/llvm/Support/SwapByteOrder.h

   1 //===- SwapByteOrder.h - Generic and optimized byte swaps -------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file declares generic and optimized functions to swap the byte order of
  10 // an integral type.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #ifndef LLVM_SUPPORT_SWAPBYTEORDER_H
  15 #define LLVM_SUPPORT_SWAPBYTEORDER_H
  16
  17 #include "llvm/Support/Compiler.h"
  18 #include "llvm/Support/DataTypes.h"
  19 #include <cstddef>
  20 #include <type_traits>
  21 #if defined(_MSC_VER) && !defined(_DEBUG)
  22 #include <stdlib.h>
  23 #endif
  24
  25 namespace llvm {
  26 namespace sys {
  27
  28 /// SwapByteOrder_16 - This function returns a byte-swapped representation of
  29 /// the 16-bit argument.
  30 inline uint16_t SwapByteOrder_16(uint16_t value) {
  31 #if defined(_MSC_VER) && !defined(_DEBUG)
  32   // The DLL version of the runtime lacks these functions (bug!?), but in a
  33   // release build they're replaced with BSWAP instructions anyway.
  34   return _byteswap_ushort(value);
  35 #else
  36   uint16_t Hi = value << 8;
  37   uint16_t Lo = value >> 8;
  38   return Hi | Lo;
  39 #endif
  40 }
  41
  42 /// SwapByteOrder_32 - This function returns a byte-swapped representation of
  43 /// the 32-bit argument.
  44 inline uint32_t SwapByteOrder_32(uint32_t value) {
  45 #if defined(__llvm__) || (LLVM_GNUC_PREREQ(4, 3, 0) && !defined(__ICC))
  46   return __builtin_bswap32(value);
  47 #elif defined(_MSC_VER) && !defined(_DEBUG)
  48   return _byteswap_ulong(value);
  49 #else
  50   uint32_t Byte0 = value & 0x000000FF;
  51   uint32_t Byte1 = value & 0x0000FF00;
  52   uint32_t Byte2 = value & 0x00FF0000;
  53   uint32_t Byte3 = value & 0xFF000000;
  54   return (Byte0 << 24) | (Byte1 << 8) | (Byte2 >> 8) | (Byte3 >> 24);
  55 #endif
  56 }
  57
  58 /// SwapByteOrder_64 - This function returns a byte-swapped representation of
  59 /// the 64-bit argument.
  60 inline uint64_t SwapByteOrder_64(uint64_t value) {
  61 #if defined(__llvm__) || (LLVM_GNUC_PREREQ(4, 3, 0) && !defined(__ICC))
  62   return __builtin_bswap64(value);
  63 #elif defined(_MSC_VER) && !defined(_DEBUG)
  64   return _byteswap_uint64(value);
  65 #else
  66   uint64_t Hi = SwapByteOrder_32(uint32_t(value));
  67   uint32_t Lo = SwapByteOrder_32(uint32_t(value >> 32));
  68   return (Hi << 32) | Lo;
  69 #endif
  70 }
  71
  72 inline unsigned char  getSwappedBytes(unsigned char C) { return C; }
  73 inline   signed char  getSwappedBytes(signed char C) { return C; }
  74 inline          char  getSwappedBytes(char C) { return C; }
  75
  76 inline unsigned short getSwappedBytes(unsigned short C) { return SwapByteOrder_16(C); }
  77 inline   signed short getSwappedBytes(  signed short C) { return SwapByteOrder_16(C); }
  78
  79 inline unsigned int   getSwappedBytes(unsigned int   C) { return SwapByteOrder_32(C); }
  80 inline   signed int   getSwappedBytes(  signed int   C) { return SwapByteOrder_32(C); }
  81
  82 #if __LONG_MAX__ == __INT_MAX__
  83 inline unsigned long  getSwappedBytes(unsigned long  C) { return SwapByteOrder_32(C); }
  84 inline   signed long  getSwappedBytes(  signed long  C) { return SwapByteOrder_32(C); }
  85 #elif __LONG_MAX__ == __LONG_LONG_MAX__
  86 inline unsigned long  getSwappedBytes(unsigned long  C) { return SwapByteOrder_64(C); }
  87 inline   signed long  getSwappedBytes(  signed long  C) { return SwapByteOrder_64(C); }
  88 #else
  89 #error "Unknown long size!"
  90 #endif
  91
  92 inline unsigned long long getSwappedBytes(unsigned long long C) {
  93   return SwapByteOrder_64(C);
  94 }
  95 inline signed long long getSwappedBytes(signed long long C) {
  96   return SwapByteOrder_64(C);
  97 }
  98
  99 inline float getSwappedBytes(float C) {
 100   union {
 101     uint32_t i;
 102     float f;
 103   } in, out;
 104   in.f = C;
 105   out.i = SwapByteOrder_32(in.i);
 106   return out.f;
 107 }
 108
 109 inline double getSwappedBytes(double C) {
 110   union {
 111     uint64_t i;
 112     double d;
 113   } in, out;
 114   in.d = C;
 115   out.i = SwapByteOrder_64(in.i);
 116   return out.d;
 117 }
 118
 119 template <typename T>
 120 inline typename std::enable_if<std::is_enum<T>::value, T>::type
 121 getSwappedBytes(T C) {
 122   return static_cast<T>(
 123       getSwappedBytes(static_cast<typename std::underlying_type<T>::type>(C)));
 124 }
 125
 126 template<typename T>
 127 inline void swapByteOrder(T &Value) {
 128   Value = getSwappedBytes(Value);
 129 }
 130
 131 } // end namespace sys
 132 } // end namespace llvm
 133
 134 #endif